In one popular kind of disk memory module, a permanent housing encloses the disk assembly (which comprises the disk itself, the hub which is mounted on and rotated by the drive unit spindle, and means for fastening the disk to the hub). An opening in the bottom of the housing allows access to the hub by the drive unit spindle. During use the disk assembly is supported by the spindle, but the housing must provide the support when the module is not mounted on the drive unit. What is important is that the disk itself not be allowed to touch the inside of the housing at any time, because damage to the recording surface may occur. This may result in loss of information and possibly catastrophic "crashing" of the disk, ruining the transducing head as well.
When the module is dismounted from the drive unit, the disk assembly is axially clamped in some fashion by a mechanism associated with the closing of an access port (e.g. U.S. Pat. No. 4,084,200) or with a dust shield attached to the bottom of the module housing. The force produced by clamping the disk assembly thusly is not great enough however, to prevent radial shifting of the disk assembly during rough handling. To prevent excessive radial shifting in this case, as well as when the assembly is loose within the housing, a typical solution has been to place cylindrical projections at spaced intervals about the periphery of the hub adjacent the spindle access opening. This has not been totally successful for several reasons. Since a relatively small amount of contact area is involved relative to the mass of the hub assembly and the low area and strength of the (usually plastic) projections, they are liable to deformation and wear over a period of time. In the cases where the dust shield attaches to the bottom of the permanent housing to clamp the hub against the upper interior surface of the permanent housing, areas of the projections which restrain radial movement of a disk assembly are even smaller.